- in the name of Allah -
Someone once asked the Prophet (saw) why he made istighfaar so often, when Allah already forgave him all of his sins. His (saw) reply was that should he not be a grateful slave to Allah.
I didn't pick up on this point till not that long ago, but the immediate and direct connection is made in his (saw) answer, linking seeking forgiveness from Allah as being equivalent to being grateful to Him. Note these are two distinct concepts. Gratitude is typically "thank you", not "forgive me". But in our relationship to Allah, all the good we do, especially the essential part of always seeking repentance, counts for us as being grateful slaves to Allah. Connecting these dots didn't click at first, but eventually the realization comes that in seeking Allah's forgiveness there is acknowledgement of one's flaws and a statement of one's constant need of Allah's help, in all aspects of life. The best way an 'abd of Allah claims his status as such is recognizing and continually making istighfaar, a kind of side course into shukr which I find amazing mA, as the obvious methods would be saying alhamdulillah, subhanAllah, etc.